One Rep Max Calculator
Calculate your one-rep max (1RM) based on submaximal lifts. Use multiple formulas (Brzycki, Epley, Lombardi) to estimate your maximum strength safely without testing your true 1RM.
Unit
Enter the weight you lifted (not your 1RM, but a weight you can lift for multiple reps).
Enter the number of reps you completed with that weight. For best accuracy, use 3-6 reps.
Different formulas may give slightly different results. Brzycki is the most commonly used formula.
Enter weight and reps above to calculate your one-rep max
Safety Warning
Table of Contents
What is One Rep Max?
Your one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a fundamental metric in strength training used to:
- Measure absolute strength
- Design training programs based on percentages of 1RM
- Track strength progress over time
- Set realistic training goals
However, testing your true 1RM can be dangerous and requires proper preparation, form, and often a spotter. That's where 1RM calculators come in — they estimate your maximum strength based on submaximal lifts (weights you can lift for multiple reps), allowing you to train safely while still knowing your estimated maximum.
Example: If you can bench press 200 lbs for 5 reps, your estimated 1RM might be around 225-230 lbs, depending on the formula used.
How it Works
Our one-rep max calculator uses mathematical formulas to estimate your 1RM based on:
- Weight lifted: The amount of weight you successfully lifted
- Number of reps: How many repetitions you completed with that weight
- Formula selection: Different formulas may give slightly different estimates
The calculator then:
- Calculates your estimated 1RM using the selected formula
- Provides training percentages (50%, 60%, 70%, 80%, 90%, 95% of 1RM)
- Shows weights for different training intensities
Best Accuracy: Formulas are most accurate when using 3-6 rep ranges. Using higher rep counts (7-10) may result in less accurate estimates.
1RM Formulas
Different researchers have developed various formulas to estimate 1RM. Each has its strengths and may give slightly different results:
Brzycki Formula (Most Popular)
1RM = weight × (36 / (37 - reps))
Developed by Matt Brzycki, this is the most widely used formula. It's simple, easy to remember, and generally accurate for most lifters.
Epley Formula
1RM = weight × (1 + reps/30)
Developed by Boyd Epley, this formula is commonly used and tends to give slightly higher estimates than Brzycki for lower rep ranges.
Lombardi Formula
1RM = weight × reps^0.10
Developed by Lombardi, this formula uses a power function and may give different results than linear formulas.
Mayhew et al. Formula
1RM = weight × (100 / (52.2 + 41.9 × e^(-0.055 × reps)))
A more complex exponential formula that may be more accurate for certain rep ranges.
O'Conner et al. Formula
1RM = weight × (1 + reps/40)
Similar to Epley but uses a different coefficient, giving slightly more conservative estimates.
Wathan Formula
1RM = weight × (100 / (48.8 + 53.8 × e^(-0.075 × reps)))
Another exponential formula that may provide different estimates for various rep ranges.
Which formula should you use? Brzycki is the most popular and generally reliable. If you want to compare, try different formulas and see which estimate aligns best with your actual performance over time.
Training Percentages
Once you know your estimated 1RM, you can use percentages of that max to design your training program:
| Percentage | Training Zone | Typical Rep Range | Purpose |
|---|---|---|---|
| 50-60% | Recovery/Endurance | 12-20+ reps | Active recovery, technique work, muscular endurance |
| 60-70% | Hypertrophy | 8-12 reps | Muscle growth, volume training |
| 70-80% | Strength | 5-8 reps | Building strength, power development |
| 80-90% | Peak Strength | 3-5 reps | Maximal strength development, peaking |
| 90-95% | Maximal Strength | 1-3 reps | Testing strength, competition prep |
| 95-100% | 1RM Testing | 1 rep | True maximum strength testing (use with caution) |
Example: If your estimated 1RM is 225 lbs:
- 70% = 157.5 lbs (good for 5-8 rep strength work)
- 80% = 180 lbs (good for 3-5 rep peak strength work)
- 90% = 202.5 lbs (good for 1-3 rep maximal strength work)
Safety Considerations
Important: One-rep max calculations are estimates, not guarantees. Always prioritize safety when lifting heavy weights.
Before Attempting Heavy Lifts
- Warm up properly with lighter weights
- Use proper form and technique
- Have a qualified spotter present
- Use safety equipment (safety bars, collars, etc.)
- Listen to your body and stop if something feels wrong
Limitations of 1RM Calculators
- Formulas are estimates, not exact measurements
- Accuracy varies by individual and exercise type
- Results may differ based on training experience
- Fatigue, nutrition, and recovery affect actual performance
- Some exercises (like deadlifts) may have different accuracy
Best Practices
- Use 3-6 rep ranges for most accurate estimates
- Test with fresh muscles (not after other heavy work)
- Use the same exercise and form as your training
- Consider multiple formulas and average the results
- Update your 1RM estimates regularly as strength changes
Common Use Cases
- Strength Training Programs: Design periodized programs based on percentages of 1RM
- Progress Tracking: Monitor strength gains over time without testing true 1RM
- Workout Planning: Determine appropriate training weights for different rep ranges
- Powerlifting: Estimate competition maxes and plan training cycles
- Bodybuilding: Calculate weights for hypertrophy training (8-12 rep ranges)
- General Fitness: Set realistic strength goals and track improvements
- Rehabilitation: Progressively increase loads during recovery
- Coaching: Help clients determine appropriate training intensities
Frequently Asked Questions
1RM calculators are estimates, not exact measurements. Accuracy depends on the rep range used (3-6 reps are most accurate), the individual's training experience, exercise type, and the formula chosen. Most formulas are accurate within ±5% when using appropriate rep ranges.
There's no single "most accurate" formula for everyone. Brzycki is the most popular and generally reliable. Different formulas may work better for different individuals, rep ranges, or exercises. Many lifters compare multiple formulas and use an average, or find which formula best matches their actual performance over time.
For best accuracy, use 3-6 reps. This range provides a good balance between accuracy and safety. Using 1-2 reps may be less accurate due to technique variations, while 7-10+ reps may underestimate your true 1RM due to fatigue factors.
Yes, but accuracy may vary. These formulas work best for compound movements like squats, bench press, and deadlifts. Isolation exercises or exercises with different movement patterns may have different accuracy. Always use the same exercise and form when testing.
Recalculate your 1RM every 4-8 weeks, or whenever you notice significant strength improvements. As you get stronger, your training weights should increase, so updating your 1RM ensures your training percentages remain accurate.
Testing your true 1RM is not necessary for most training goals and can be risky. Use estimates from submaximal lifts instead. Only attempt a true 1RM if you're an experienced lifter, have proper form, have a spotter, and are preparing for competition. Always prioritize safety over testing maximum strength.
This is normal. Different formulas use different mathematical approaches and may give slightly different estimates. You can average multiple formulas, or track which formula best matches your actual performance over time. For most purposes, any of the formulas will give you a useful estimate for training.